This paper presents finding of how liquid hydrocarbon carryover from production separators could form solid contaminants that would later become a root cause for an unexpected failure of tri-ethylene glycol gas dehydration unit to deliver dry export gas. This incident will later be followed by an unanticipated capillary aided gas hydrate blockage inside the gas export line during a planned maintenance shut-down. Upon detailed operational review, all section of TEG dehydration tower unit are opened up, and inspected for: (1) presence of any solid contamination and blockages, and (2) to evaluate presence of internal equipment damages inside the dehydration system. Observations are explained with data analysis and field images, while correlating to TEG dehydration unit's operating parameters; pre and post gas hydrate blockage incident. Compositional analysis using GC-FID, XRD and EDS are conducted on samples collected from the unit to understand its nature. Then, using a customized gas hydrate rocking cell apparatus, gas hydrates growths are observed under 8 °C sub-cooling temperature. From vessel inspection, it is found that liquid hydrocarbon carryover results in accumulation of high chain hydrocarbon deposits (C19-C36), and some mineral scales formation inside the unit. These deposits are found to form when liquid carry-over passes through the reboiler unit. This then gradually blocks the TEG distribution spray nozzles and reduces the efficiency of gas dehydration. Later, with only 20.5% of the spray nozzle found to be in working condition, the dP across the distribution bar exceeds its maximum operating limit, later causing it to split open along the weldment area. Hence, this results a total functional failure to deliver dry gas, and formation of gas hydrate blockage later. On the basis of detailed operational review, field testing, compositional analysis and hydrate growth observations, the sequence of events that later caused a catastrophic capillary aided gas hydrate blockage even in the presence of hydrate risk management program is presented in this paper.
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Offshore Technology Conference Asia
March 20–23, 2018
Kuala Lumpur, Malaysia
ISBN:
978-1-61399-552-5
Unconventional Gas Dehydration System Failure Resulting in a Gas Hydrate Blockage
J. D. Sundramoorthy;
J. D. Sundramoorthy
Baker Hughes a GE Company
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K. Moodley
K. Moodley
SBM Joint Venture Malaysia Deepwater Contractors, MDPC
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Paper presented at the Offshore Technology Conference Asia, Kuala Lumpur, Malaysia, March 2018.
Paper Number:
OTC-28379-MS
Published:
March 20 2018
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Citation
Sundramoorthy, J. D., Leknes, M. J., and K. Moodley. "Unconventional Gas Dehydration System Failure Resulting in a Gas Hydrate Blockage." Paper presented at the Offshore Technology Conference Asia, Kuala Lumpur, Malaysia, March 2018. doi: https://doi.org/10.4043/28379-MS
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